Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$130.42	5.616%	$137.7444	$137.74	$137.75	$137.70
Purchase #2	$135.61	5.222%	$142.6916	$142.69	$142.70	$142.70
Purchase #3	$144.33	4.328%	$150.5766	$150.58	$150.60	$150.60
Purchase #4	$40.56	5.396%	$42.7486	$42.75	$42.75	$42.70
Purchase #5	$184.68	6.528%	$196.7359	$196.74	$196.75	$196.70
Purchase #6	$134.36	13.206%	$152.1036	$152.10	$152.10	$152.10
Purchase #7	$80.98	4.290%	$84.454	$84.45	$84.45	$84.50
7 purchase totals =	$850.94		$907.0547	$907.05	$907.10	$907.00